In the sixth report by Dame Janet, his years as a junior doctor at Pontefract General Infirmary in the early 70s came under the spotlight.

"There is some evidence that he liked to 'test the boundaries' of certain forms of treatment," she said.

Dame Janet added: "It is quite likely that some of the deaths Shipman caused resulted from experimentation with drugs."

She said Shipman's own drug habit could have started while he was at PGI.

Some regarded him as strange, sinister, odd

Dame Janet Smith

It was also probable that his abuse of the drug pethidine - to which he later became addicted - could have started when he worked in the obstetrics unit, the report said.

Dame Janet said that as early as 1971 he was showing the traits he later demonstrated during his sustained killing spree as a GP in Hyde.

She said the way he tried to "ingratiate" himself with people in authority reminded her of the way he later ingratiated himself with Ghislaine Brant, manager of the pharmacy next to his surgery in Hyde, to get supplies of the drug diamorphine without question.

'Unusual entries

Dame Janet said the high proportion of deaths registered by Shipman as being a sudden death by stroke were similar to the causes of death he registered killing his patients in Hyde.

An analysis showed Shipman signed an abnormally high number of death certificates between 1800 and midnight in hospital which could not be explained clinically.

Dame Janet said this suggested he "might have been hastening the deaths of patients who were very close to death and who might otherwise have died a few hours later."

Shipman also made "unusual" entries in the patient medical records about their deaths which were either "very short or over-elaborate or contain crossings out."

'Hasten death'

Again these were similar to entries in records when he killed in Hyde.

Dame Janet said there was a strong suspicion Shipman hastened the death of four-year-old Susan Garfitt in PGI because it happened "so soon" after her mother said she did not want to prolong her daughter's suffering and told Shipman to be "kind" to her.

Ten minutes after she went for a cup of tea she found her daughter dead.

"She certainly did not give permission for Shipman to do anything to hasten Susie's death," Dame Janet said.